U.S. Pat. No. 3,831,759, assigned to the assignee of the present invention, discloses and covers a filter device for filtering liquids comprising a reservoir member for receiving the liquid to be filtered and a spout member for exit of the liquid after it is filtered, these members being assembled with a filter disc therebetween, one of the members being provided with an annular magnet and the other of the members being provided with an annular magnet or an annulus of other ferromagnetic material such that the magnetic attraction sealingly clamps the filter disc between the members during the filtration. The filter devices of this patent are in common use and have provided successful and advantageous particularly in that they enable rapid assembly and disassembly desired for insertion and removal of the filter disc and yet with a good seal between the filter disc and the reservoir and spout members during filtration. A problem, however, has been that the magnetic and ferromagnetic materials are subject to deterioration. Such deterioration can be from corrosion due to contact with acidic or other corrosive liquids or from chipping or cracking where ceramic magnets are used. The latter in particular is a problem in that ceramic magnets, such as of the alkaline metal or alkaline earth metal ferrites, while otherwise being excellent because of their light weight, relatively low cost and high magnetic strength, are disadvantageous by reason of their susceptibility to chipping or cracking.
The present invention is an improvement over that covered by the aforesaid patent, an improvement wherein ceramic magnets are used so as to gain their fullest advantages and yet with the structure of the filtration device being such that the disadvantages are eliminated.